Wind Power
In recent years wind power has become one of the fastest growing means for generating electricity. The main reason for this is that it is seen as less problematic than most of the other alternative energy sources out there. For years solar power was thought likely to be the best bet as an alternative fuel source. However there are a number of problems that need to be overcome for solar power to become more widely used. Admittedly there are a issues that will need to be addressed for wind power as well but they are thought to be more likely to be overcome than those facing solar power.
The biggest problem that is facing wind power is that it is not available on a consistent basis. Some days the wind will be very strong and others it will be nonexistent. This is an issue with solar power as well but at least in that case you know that it won't be available at night. Unfortunately weather forecasting isn't to the point that you can predict the strength of the wind more than a few days in advance. This means that you are either going to have to figure out a way to save excess power from days when the wind is strong or you are going to have to have an alternative source of power for calm days. Right now wind power is used almost exclusively as a supplement to other forms of power. That makes it easy to continue to generate electricity through other means on days when there is no wind. However if wind is ever going to supplant these other forms of energy this problem will need to be overcome.
The other big problem with wind power is cost. While it costs very little to actually generate electricity with a wind farm the costs of building one are very high. In most cases it has required massive government subsidies in order to get wind farms built. The cost has been coming down in terms of building wind farms and they are no getting to the point where the total cost of generating electricity with the wind including both capital and operating costs is now almost the same as other forms of generation. Unfortunately there is another cost to wind power that needs to be factored in and will seriously limit the growth of wind power.
The other big problem with wind power is that wind farms need to be built in areas with lots of open space. This limits the number of places that you can build them. It also affects the ability to use the land for other purposes. For example most of the open space that would be ideal for a wind farm is currently be used for agriculture. However the biggest problem is that since wind farms need to be built in big open spaces they are usually located a long way from the population centers that needs the electricity. This means a whole new power grid will need to be built at a very high cost.